From the FAQ page of the U.S. Copyright Office:
"Copyright does not protect ideas, concepts, systems, or methods of doing something. You may express your ideas in writing or drawings and claim copyright in your description, but be aware that copyright will not protect the idea itself as revealed in your written or artistic work."
http://www.copyright.gov/help/faq/fa...l#what_protect
Lots of info at their home site:
http://www.copyright.gov/